Using curl_multi_add_handle() in PHP to Manage Multiple cURL Requests

In PHP network request development, the curl library is a commonly used tool that offers many functions for performing various HTTP requests such as GET and POST, setting request headers, and handling cookies.

When sending multiple requests simultaneously, creating a separate cURL handle for each request can waste resources. PHP provides the curl_multi_add_handle() function to add multiple cURL handles to a single session for efficient management.

The syntax of curl_multi_add_handle() is:

resource curl_multi_add_handle ( resource $mh , resource $ch )

Parameters: $mh: an initialized cURL multi session handle. $ch: the new cURL handle to be added to the multi session.

The function adds the $ch handle to the $mh multi handle and returns a cURL multi handle.

Below is a sample code using curl_multi_add_handle():

<?php
$mh = curl_multi_init();  // Initialize a cURL multi session

$ch1 = curl_init();
curl_setopt($ch1, CURLOPT_URL, "https://www.example.com/api1");
curl_setopt($ch1, CURLOPT_RETURNTRANSFER, true);
curl_multi_add_handle($mh, $ch1);  // Add first handle

$ch2 = curl_init();
curl_setopt($ch2, CURLOPT_URL, "https://www.example.com/api2");
curl_setopt($ch2, CURLOPT_RETURNTRANSFER, true);
curl_multi_add_handle($mh, $ch2);  // Add second handle

// Execute until all requests are complete
do {
    $status = curl_multi_exec($mh, $running);
} while ($status === CURLM_CALL_MULTI_PERFORM || $running);

// Retrieve results
$response1 = curl_multi_getcontent($ch1);
echo "Response 1: " . $response1 . "
";
$response2 = curl_multi_getcontent($ch2);
echo "Response 2: " . $response2 . "
";

// Clean up
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);
?>

The example first initializes a multi handle with curl_multi_init(), creates two independent cURL handles ( $ch1 and $ch2), sets their URLs and options, and adds them to the multi session using curl_multi_add_handle(). It then loops with curl_multi_exec() until all requests finish, retrieves each response with curl_multi_getcontent(), and finally removes the handles and closes the session.

Using curl_multi_add_handle() efficiently manages multiple cURL handles, improving network request performance and code maintainability. In practice, it can be combined with other functions such as curl_multi_remove_handle() and curl_multi_close() for more complex request workflows.

In summary, the curl_multi_add_handle() function is a valuable tool for adding multiple cURL handles to a single session, thereby enhancing request efficiency and code maintainability in real‑world development.